Downregulation of COP9 signalosome subunits differentially affects the CSN complex and target protein stability

The transcription factor interferon regulatory factor 5 (IRF5) exerts crucial functions in the regulation of host immunity against extracellular pathogens, DNA damage-induced apoptosis, death receptor signaling, and macrophage polarization. Tight regulation of IRF5 is thus warranted for an efficient response toward extracellular stressors and for limiting autoimmune and inflammatory responses. Here we report that the COP9 signalosome (CSN), a general modulator of diverse cellular and developmental processes, associates constitutively with IRF5 and promotes its protein stability. The constitutive CSN/IRF5 interaction was identified using proteomics and confirmed by endogenous immunoprecipitations. The CSN/IRF5 interaction occurred on the carboxyl and amino termini of IRF5; a single internal deletion from amino acids 455 to 466 (⌬455-466) was found to significantly reduce IRF5 protein stability. CSN subunit 3 (CSN3) was identified as a direct interacting partner of IRF5, and knockdown of this subunit with small interfering RNAs resulted in enhanced degradation. Degradation was further augmented by knockdown of CSN1 and CSN3 together. The ubiquitin E1 inhibitor UBEI-41 or the proteasome inhibitor MG132 prevented IRF5 degradation, supporting the idea that its stability is regulated by the ubiquitin-proteasome system. Importantly, activation of IRF5 by the death receptor ligand tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) resulted in enhanced degradation via loss of the CSN/IRF5 interaction. This study defines CSN to be a new interacting partner of IRF5 that controls its stability.

show abstract

“…1B). Little is known of CSN4 function in mammalian cells, yet CSN4 to CSN7 have previously been designated a mini-CSN subcomplex (50).…”

Section: Resultsmentioning

confidence: 99%

“…As a negative control, we examined whether knockdown of another COP9 subunit, CSN5, which does not directly interact with IRF5 (Fig. 3) or affect the CSN complex (50), would have an effect on IRF5 stability. Data in Fig.…”

Section: Figmentioning

confidence: 99%

The COP9 Signalosome Interacts with and Regulates Interferon Regulatory Factor 5 Protein Stability

Korczeniewska

Barnes

2013

Molecular and Cellular Biology

View full text Add to dashboard Cite

show abstract

“…CSN1 is known to play a crucial role in the integrity of the CSN complex (37,(39)(40)(41). To identify functionally important regions in CSN1, we mapped the sequence similarity score onto the surface of the atCSN1 crystal structure (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The atCSN1, encoded in the chromosome 3, has 441 amino acids that are 45% identical in sequence to Homo sapiens CSN1. Among all of the subunits of the complex, CSN1 is known to be the longest and to play a crucial role in complex integrity (39)(40)(41). Here, we report the crystal structure of atCSN1 and describe its integration within the complex as well as its interaction with IκBα in the NF-κB signaling pathway.…”

mentioning

confidence: 99%

Crystal structure and versatile functional roles of the COP9 signalosome subunit 1

Lee

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

The constitutive photomorphogenesis 9 (COP9) signalosome (CSN) plays key roles in many biological processes, such as repression of photomorphogenesis in plants and protein subcellular localization, DNA-damage response, and NF-κB activation in mammals. It is an evolutionarily conserved eight-protein complex with subunits CSN1 to CSN8 named following the descending order of molecular weights. Here, we report the crystal structure of the largest CSN subunit, CSN1 from Arabidopsis thaliana (atCSN1), which belongs to the Proteasome, COP9 signalosome, Initiation factor 3 (PCI) domain containing CSN subunit family, at 2.7 Å resolution. In contrast to previous predictions and distinct from the PCI-containing 26S proteasome regulatory particle subunit Rpn6 structure, the atCSN1 structure reveals an overall globular fold, with four domains consisting of helical repeat-I, linker helix, helical repeat-II, and the C-terminal PCI domain. Our small-angle X-ray scattering envelope of the CSN1-CSN7 complex agrees with the EM structure of the CSN alone (apo-CSN) and suggests that the PCI end of each molecule may mediate the interaction. Fitting of the CSN1 structure into the CSN-Skp1-Cul1-Fbox (SCF) EM structure shows that the PCI domain of CSN1 situates at the hub of the CSN for interaction with several other subunits whereas the linker helix and helical repeat-II of CSN1 contacts SCF using a conserved surface patch. Furthermore, we show that, in human, the C-terminal tail of CSN1, a segment not included in our crystal structure, interacts with IκBα in the NF-κB pathway. Therefore, the CSN complex uses multiple mechanisms to hinder NF-κB activation, a principle likely to hold true for its regulation of many other targets and pathways.T he constitutive photomorphogenesis 9 (COP9) signalosome (CSN) is a more than 300-kDa complex that was first identified as a negative regulator of Constitutive Photomorphogenesis (COP) in plants (1, 2). In the subsequent years, the highly conserved protein complex was also found in fungi (3, 4), Caenorhabditis elegans (5), Drosophila melanogaster (6), and mammals (7,8). The most studied function of the CSN complex in eukaryotes is the regulation of protein degradation through two pathways, deneddylation (9-11) and deubiquitination (12, 13). In the deneddylation pathway, the CSN complex can influence the cullin-RING ligase activity by removing Nedd8, a ubiquitin-like protein, from a cullin (9, 14). On the other hand, the CSN complex can also suppress cullin activity through recruitment of the deubiquitination enzyme USP15 (12) or Ubp12p, the Schizosaccharomyces pombe ortholog of human USP15 (13). Other functions of the CSN complex identified in mammalian cells include regulating the phosphorylation of ubiquitin-proteasome pathway substrates through CSN-associated kinases (7,(15)(16)(17)(18). Overall, the CSN complex appears to be a key player in protein subcellular localization (19,20), DNA-damage response (21), NF-κB activation (22), development, and cell cycle control (23,24). Thus, the functions ...

show abstract

“…Csn5-f was recently shown to interact with cyclin-dependent kinase CDK2 (32). It was reported that in Csn5 hypo- morphic cells such as siRNA-mediated Csn5 knockdown cells, Csn5-f-or Csn5-containing small complexes were decreased more drastically than the CSN-associated form of Csn5 (31,43,44). To investigate how Csn8 hypomorphism affects the distribution of Csn5 proteins between CSN-associated and Csn5-f populations, the Csn8 h or Csn8 ϩ MEF cell extracts were fractionated through a Superose-6 gel filtration column (Fig.…”

Section: When Comparing Different Csn8mentioning

confidence: 99%

COP9 Signalosome Subunit Csn8 Is Involved in Maintaining Proper Duration of the G1 Phase

Liu

Menon

et al. 2013

Journal of Biological Chemistry

View full text Add to dashboard Cite

Background: Among the eight subunits of the COP9 signalosome (CSN), Csn8 is only present in higher eukaryotes. Results: Decreases in Csn8 accelerate cell growth and shorten G 1 duration, whereas decreases in Csn5 impair cell proliferation. Conclusion: Although Csn5 promotes cell proliferation, Csn8 negatively regulates G 1 progression. Significance: The dynamics of CSN are an important factor influencing cell division and differentiation.

show abstract

Downregulation of COP9 signalosome subunits differentially affects the CSN complex and target protein stability

Cited by 57 publications

References 36 publications

The COP9 Signalosome Interacts with and Regulates Interferon Regulatory Factor 5 Protein Stability

The COP9 Signalosome Interacts with and Regulates Interferon Regulatory Factor 5 Protein Stability

Crystal structure and versatile functional roles of the COP9 signalosome subunit 1

COP9 Signalosome Subunit Csn8 Is Involved in Maintaining Proper Duration of the G1 Phase

Contact Info

Product

Resources

About